Anchor Work

7/31/2019 Anchor Work

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M.S. RAI MASTER ORAL MAY 2012

ANCHOR WORK

The anchor planShips Master/Captain or Offshore Installation Manager (OIM), the Officer inCharge It would be expected that these key personnel would inform relevantcrew members through an established chain of command, regarding relevantcriteria.In the construction of any anchor plan the following items must be worthy of

consideration:

The intended position of anchoring of the vessel. The available swinging room at the intended position. The depth of water at the position, at both High and Low water times. That the defined position is clear of through traffic. That a reasonable degree of shelter is provided at the intended position. The holding ground for the anchor is good and will not lend to dragging. The position as charted is free of any underwater obstructions. The greatest rate of current in the intended area of the anchorage. The arrival draught of the vessel in comparison with the lowest depth to

ensure adequate underkeel clearance.

The choice of anchor(s) to be used. Whether to go to single anchor or an alternative mooring. The position of the anchor at point of release. The amount of cable to pay out (scope based on several variables). The ships course of approach towards the anchorage position. The ships speed of approach towards the anchorage position.

Defined positions of stopping engines, and operating astern propulsion(SingleAnchor Operation).

Position monitoring systems confirmed. State of tide ebb/flood determined for the time of anchoring. Weather forecast obtained prior to closing the anchorage. Time to engage manual steering established. When anchoring the vessel, it would be the usual practice to have

communications by way of anchor signals prepared for day and/or nightscenarios. Port and harbor authorities may also have to be kept informedif the anchorage is inside harbor limits or inside national waters.

NB. Masters, or Officers in Charge, should consider that taking the vessel

into an anchoragemust be considered a Bridge Team operation.

ANCHOR OPERATIONS AND DEPLOYMENT

Bringing the vessel to a single anchor It would be normal procedure for a ships master to consider the

approach towards an anchorage, and discuss the operation with theOfficer in Charge of the anchor party, namely the Chief Officer of the


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vessel. Probably the most common of all uses of anchors is to bring avessel into what is known as a single anchor where the ship has

adequate swinging room to turn about her one anchor position, with theturn of the tide and/or influence of the prevailing weather.

Aplanned approach to the intended position should be employed with the

Master or Marine Pilot holding the con of the vessel.The anchor party, on the orders of the Master, should clear away theanchor lashings and walk back the intended anchor for use in ampletime, before the vessel reaches the anchor position. The readiness of theanchor to be Let Go should be communicated to the bridge by theintercom/ phone system or Walkie Talkie radio. The Master would turnthe vessel into a position of stemming the tide and manoeuvre the shiptowards that position (as per plan) where he intends to let go theanchor.By necessity, the ship will still be making headway in order to attainthis position. Headway is taken off at this point by using astern

propulsion but it will be noticed that sternway will not take an immediate

effect (masters will have to estimate when the vessel is moving asternand this is not always readily observed. One method is to sight the wakefrom the propeller moving past the midships point towards the forwardpart of the vessel. This is a positive indication that sternway is on

thevessel).

Fundamental principle of anchoring, is that it is the weight of cable

and the lay of the scope that anchors the vessel successfully, notjust the weight or design ofthe anchor.

Once sternway is positively identified on the vessel, and the position ofletting go the anchor is achieved, the Master would order the anchor to

be released. The astern movement of engines would be reduced to anamount that the anchor cable could be payed out on the windlass brake,as the vessel continues to drop astern, slowly.

The Officer in Charge of the anchor party would check the run of cableby using the gypsy braking system in order to achieve a lay of cablelength along the sea bed. The

Officer in Charge would endeavour not to pile the cable in a heap on topof, or close to, the anchor position. As the pre-determined amount ofcable to be released is achieved, the engines should be stopped from

moving astern. The cable will have been

allowed to run and the brake would then be applied to check the amountof scope. This should serve the purpose of digging the anchor into thesea bed and stop the vessel moving any further astern, over the ground.The ship is described as beingBrought Up to her anchor and it would bethe duty of the anchor party officer to determine when the vessel isbrought up and not dragging her anchor.


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Amount of anchor cable to use (single anchor)

The experience of the Master will always influence the amount of anchor cableto be employed for a single anchor operation. Most masters would work on the

premise that 4 _ Depth of water would be considered as the absolute minimum.

The nature of the holding ground, the range and strength of tide, the currentand expected weather conditions will all be factors that influence the optimumscope The intended time period of staying at anchor would be a further factor.When all the variables are considered the Master would still probably addanother shackle length for luck and ship security.Clearly the available swingingroom must reflect the scope of cable and keep the vessel clear of surfaceobstructions.Consideration of the amount of cable to use would be made well before the

approach is made to the anchorage; the amount being establishedfollowing a chart assessment of the intended anchorage and an

assessment of all variable factors which could affect the safety of the

vessel. The use of a comprehensiveanchor plan in the form of a checklistcould be seen as beneficial and is considered good practice within someshipping companies.

Swinging roomvessel lying to a single anchor

Surface obstructions must be significantly clear of the swinging circle, e.g.piers, buoys, navigation marks, etc.

Swinging room for a vessel at the single anchor will occur at themaximum scope of cable when at long stay. This circle of swing could be

practically reduced by employing

two anchors in the form of either a running or standing moor. Althoughthese moorings are not generally common they are suitable when a large

swinging circle is not permitted like within a canal or river, where searoom is restricted.

The vessel will swing through 180 with each turn of the tide (usuallyabout every 6 hours). Movement of the vessel at anchor will also beinfluenced by the direction of wind. It is significant that wind over tideproduces a powerful effect on the cable and, depending on the nature ofthe holding ground, may cause the anchor to break out and allow thevessel to drag her anchor, an extremely undesirable situation.

Watch Officers should be cautious to any traffic movement within thecircle of swing, especially of traffic attempting to cross the ships bow.Such traffic would bedirectly affected by the same direction oftide/current and be caused to set down onthe anchor cable.

Operational safety when anchoring

Certain precautions when anchoring may seem obvious to theexperienced seafarer. However, when dealing with five (5), ten (10) ortwenty (20) tonne plus anchors, complacencycan be the seamans worstenemy. Routine operations should therefore include the following items:


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Always check that the overside surface area is clear of small craft orother obstructions under the flare of the bow, at the intended area ofletting go the anchor.

Routine operations should provide adequate time to walk the anchorback clear of the Hawse Pipe, prior to actually letting go.

Designated, experienced persons should operate the windlass andbraking system. They should also be protected by suitable clothing including hard hat

and eye goggles.

All parties to the operation should have inter-related communications.These should be tested prior to employing the ships anchors. In the caseof walkietalkie radios being used, these should operate on a clearly

identified shipboard frequency and seen not to interfere with other localshipping operations.

The marine pilot or ships Master who has the con of the vessel shouldbe continually informed as to the Lead of Cable and the number of

shackles in use. It would also be expected that the Officer in Charge ofthe anchor party would keep the bridge informed of any untowardoccurrence, e.g. fouled anchor or windlass/power defects.

All recognition and sound signals should be employed promptly andcorrectly to highlight the status of the vessel.

NB. It is expected that, when anchors are to be deployed, a riskassessment would be conducted prior to involving personnel and operatingdeck machinery.In the event that overside work is required inconjunction with the anchor operation,a permit to work, must becompleted in addition to the risk assessment.

The watch at anchor

It should be clearly understood by any and all watchkeeping personnel,that when the vessel goes to anchor, she is still considered at sea. Assuch, an effective and proper lookout must continue to be kept from thenavigation bridge. The officer of the anchor watch will be responsibledirectly to the ships Master for the well being of the ship, and should befamiliar with the two greatest dangers, namely:

o own ship dragging anchor oro another ship dragging towards own ship.

In either of these cases the Master would be expected to come to thebridge and take the con of the vessel.

Watch duties, inclusive of keeping the lookout, would expect to includemonitoring the performance of the weather particularly closely; keeping alistening watch for radio traffic and ensuring that the vessel displays the

correct navigation signal in all states of visibility. Where small launch ortender traffic is in attendance, the monitoring of movements of suchtraffic is considered good ship keeping practice.


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Other hazards also inherent to anchoring and something the diligenceof watch personnel can go some way to defend againstare: fire, piracy,collision from another vessel, pollution, dragging and shifting position.

NB. Similar duties would be expected if the vessel is moored up to mooring

buoys.

Anchoring principles

The amount of anchor cable employed has always been considered thecritical factor when bringing a vessel into an anchorage. The anchor itselfacts as a holding point from which the cable can be laid in a line on thesea bed. Ideally, this line should be at a narrow angle from the sea bed togenerate a near horizontal direction of pull onthe anchor; the positionlending to the term Long stay. Short stay is usually where the cable is atan acute angle to the surface and such a deployment would have atendency to pull the anchor upwards, possibly causing itto break its

holding of the surface at the sea bed. Direction of weight on theanchor isto cause the flukesand arms to break the surface of the holding groundwhen at short stay Direction of weight on the anchor is to cause theflukes and arms to dig in when the cable is laid horizontally on the seabed surface

Detection of dragging anchorOne of the fundamental principles of the anchor watch is to ensure that the

vessel does not break her anchor out and drag away from the anchorposition. To this end, the weather conditions, state of currents and tides

should be continuously monitored throughout the watch period. Normal

procedure for the watch officer at anchor would be to regularly verify theships position. Where dragging is suspected, the ships position would beexpectedto change.

Such movement may be ascertained by any or all of the following method

Check the anchor bearings of the fixed landmarks. These referencesshould be retained on the chart during the period of the anchorage; theyshould also be entered in the ships deck logbook. If they are changing,the ships position is changing and the vessel must be assumed to be

dragging.

Obtain an immediate positional check from the GPS operation, to ensurethat the instrument co-ordinates correspond to the Latitude andLongitude of the ships anchored position. Any discrepancy in position,

the vessel must be assumed to be dragging its anchor.

Engage the variable range marker of the ships radar onto a fixed landobject. If the range between ship and landmark opens or closes then thevessel can be assumed to be dragging its anchor.


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Direct observation and hand contact with the anchor cable may givefurther indication that the ship is dragging its anchor. Adragging anchorwould usually generate excessive vibration through the length of thecable, which could also indicate dragging (depending on the nature of theholding ground).

NB. Watch officers should not leave the navigation bridge unattended and,if checking anchor cable by this method, should wait to be relieved by themaster or another watch officer.

A hand lead over the bridge wing with the lead on the sea bed. If thevessel was dragging its anchor the lead of the line to the lead wouldstretch forward towards the position of the anchor, indicating that theship was dragging its anchor. The use of beam transit bearings is alsoconsidered as a good indicator that the vessel may be dragging her

anchor. However, the use of transits alone should not be accepted asbeing totally reliable, and would normally be used in conjunction withother methods of ascertaining movement in the ships position.

Vessel dragging towards own ship

(It must be anticipated that the ships Master would take the conn of thevessel, for such an incident.) It is not unusual for vessels to share a

common anchorage, and the additional concern for any Master or watchofficer would also be to monitor movement of other ships in and around

the anchorage. Where weather or tidal conditions are tenuous thepossibility always exists of another ship breaking its anchor out anddragging towards your own position. Such an occurrence would besomewhat out of your control and the very least that an individual cando is raise the alarm and draw attentionto the other vessel(s) of the

developing situation. There is no one affective method to in daylight

or during the hours of darkness and as such the methods to highlightthe dangermust include any or all of the following:

o Raise the effected vessel by name on the VHF radio, to advise ofthe movement(VHF should not be employed without stationidentification).

o Give five or more short and rapid blasts on own ships whistle.o Give five or more short flashes on own ships signal lamp, directed

to the effected ship.

o Display the signal RB 1 in the international code to signify: Youappear to be dragging your anchor (by day).

o Employ the ships searchlight, directed towards the vessel draggingher anchor.

Used in conjunction with Regulation 36 of the COLREGS. Action by own vessel when a ship is seen to be dragging towards your

own position

would be dependent on the time available to take action. The shipsengines would be expected to be on stop and ready for immediate


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manoeuvre, should they be required. Steaming over your own anchorcable may become a necessity to avoid contact with the vessel dragging.

Alternatively, placing the rudder hard over could give the vessel a sheerto angle ones own ship, away from a position of contact. Cable

operations of either shortening or veering ones own ships anchor cable

may provide sufficient clearance to avoid contact. To this end an anchorparty should be placed at a state of readiness as soon as the situation isrealized.Should the incident occur in conditions of poor visibility, vesselsmay also give an additional signal of one short, one prolonged, one shortblasts, to give warning of her own position to other vessels. Your ownvessel is faced with limiting options as the weight of anchors and cablesdeployed at the fore end will generally restrict vessel movement. Anastern motionwould also place excessive strain on cables and steamingover the cable would probably be seen as a preferable option, ifconsidered necessary to engage engines to avoid contact

TO APPROACH AN ANCHORAGE USING RADAR BRG GROUNDSTABILIZER


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What is Dredging an anchor ?Towing an anchor at short stay in order to improve manoeuvrability is

sometimes called dredging an anchor. For example, when going alongside in an

offshore wind, or when passing through a narrow entrance where there is a

strong cross-stream, the ship lets go the anchor at slow speed as she

approaches, and drags it along the bottom. This has the dual effect of

enhancing the control of the bow and of holding it upwind or upstream. Care

must be taken to ensure that no underwater cables or submerged equipment

are in the vicinity

Open moor

Vessel anchored with both anchors leading ahead.

Both the anchors remain 1point on the bow.


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ProceduresApproach the anchorage with wind or current on one bow.

Weather anchor or upstream anchor is let go on the run (1).

The headway continued and cable is laid up 1/3 rd of the final length

of the cable.The second anchor is let go (2).

First anchor snubbed at the gypsy.

The vessel brings-to on her weather cable. It gradually grows taut

to windward.Bow develops a rapid swing into the stream or wind.

Both the anchors are veered.

Finally the anchors are one point at each bow.

Standing moor, ordinary moor, dropping moor, straight moor

Vessel required to moor with bridge along the dotted line.

Stream ahead.


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Port anchor-5 shackles, stbd anchor-4 shackles.

Procedure:

Head to stream or wind.

When both are present, head to one has stronger effect.

With sufficient headway, take vessel to position 1.

Position-1 is roughly 5 shackles minus half ship's length beyond line AB.

Let go port anchor.

The vessel drifts downstream,renderport cable to nine shackles, the sum of two

lengths.

She is brought up on her cable.

Then the starboard anchor is let go at position-2.

Vessel then moves to the position byrenderingor veering the starboard cable and

heaving in four shackles on the riding cable.

Engines may be used to reduce stress on the windlass.

Running moor, flying moor

Vessel required to moor with bridge along the dotted line.
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Stream ahead.

Port anchor-5 shackles, starboard anchor-4 shackles.

Procedure:

Head to stream or wind.

When both are present, head to one has stronger effect.

Let go starboard anchor on run, when vessel is 4 shackles and half of ship's length (1).

The cable is rendered as the vessel moves upstream.

The cable is not allowed to be tighten, as bow will cant to starboard.

The cable is rendered or veered 9 shackles and vessel moves to position-2.

In position-2, port anchor is let go.

The vessel moves stern.

Five shackles weighed on lee (starboard) cable and five shackles veered on riding cable.

The vessel is then brought up on her riding cable at position-3.

Advantages of mooring


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Vessel occupies little swinging room.

Vessel turns almost to her length about stem.

Scopes can be pre-adjusted for the prevailing strength of wind or stream.

Scope of each cable is estimated inthe same way as single anchor.

Disadvantages

Lee anchor has no value to ship if headwind increases or vessel drags.

Risk of getting a foul hawse.

Special precautions

Maintain a constant watch to prevent foul hawse.

Determine foul arc and clear arc.

Vessel should always swing to clear arc on each tidal change.

Use engine to give vessel correct sheer.

Keep eye on the weather.

Know the times of tide change.
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Preference:I will prefer standing moor. Because:

Safer

More control on the ship.

The anchor is let go after vessel stopped.

There is no possibility of damage due to anchoring at headway.

Baltic moor

Employed alongside a quay.

Used when construction of the berth is no sufficiently strong enough to withstand

ranging in bad weather.

Can be employed for berthing a vessel in an onshore gale wind.

Procedures:For a average size merchant ship, a 25-30mm wire is passed from the after ends

on the poop, along the offshore side, outside and clear of everything.

Offshore anchor is cockbilled.

A man is send overside on a chair to secure the wire with the anchor, preferably

at the shackle.

The wire is secured with ship's rail by sail twine in bights.

The aft end of the wire is sent to a wrapping barrel, ready for heaving slack wire.

When the stem is abreast the position of the quay where the bridge will be

positioned, the anchor is let go.

The vessel is still on headway.

About half a ship's length of the cable, the cable is surged and then snubbed.

The wire is hove-in aft.


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The onshore wind will drift the vessel to the berth.

The scope of the cable and the wire is adjusted and veered slowly until the ship is

alongside.

Distance of ship, length of cable and wire must be considered.

Normally, the anchor is dropped at a distance 2/3 shackles length of the cable

from the quay, which may vary depending on the prevailing circumstance.

Mediterranean moor

Method of securing a vessel stern to the berth.

Both the anchors leading ahead to hold the bow in position.

The approach should preferably be made with the berth on port side.

The starboard anchor is let go about two ships length from the berth(1).

The vessel continues to move ahead.


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Starboard helm is applied and the cable is veered.

The engines are then put astern and the port anchor is let go (2).

As the vessel comes astern, transverse thrust swings the stern to port towards

the berth.

Stern lines are sent away.

TURNING SHORT ROUND WITH AHEAD RIVER STEM


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TURNING SHORT ROUND WITH ASTERN RIVER STEM

Anchor Work

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